Chapter 88-48.2.3 Detecting the Passage of Paper8.2.3.1 Detecting the Passage of Paper 0017-5477The paper passage detection mechanism of the fixing unit is shown below.F-8-4If a delay jam is detected by the fixing delivery sensor (SR202), the fixing motor is stopped immediately to prevent paper from winding around the fixing roller.8.3 Protective Functions8.3.1 Protective Functions 0017-9324F-8-5Protection FunctionsThis machine is provided with the following four protection functions to prevent the fixing heater from overheating:1) The CPU monitors the thermistor (TH1) voltage. If the thermistor (TH1) voltage is abnormal, the CPU judges that the fixing heater is faulty and turns off therelay (RL1). At the same time, the CPU notifies the DC controller of occurrence of the fixing heater failure.2) If the temperature of the fixing heater rises abnormally and the thermistor (TH1) detects a voltage lower than about 0.7 V (equivalent of 240 deg C), the fixingheater high temperature detection circuit cuts off the power supplied to the fixing heater.3) If the temperature of the fixing heater rises abnormally and the thermo switch (TP1) detects a temperature higher than 250 deg C, the thermo switch turns offto cuts off the power supplied to the fixing heater.EXP_P_SNSJ217-12SR502DC Controller PCBRelaycircuitFixing unitP1NF NFASICCPUZero crossingcircuitHeater drive circuit J11-16J215-2RLDRVH1DRV-13 -5H2DRV-12 -6J11-15J215-3ZEROXPower supply PCB DC Controller PCBACDCF1 F2SW1J217-6GNDGNDS_TH-5-4GNDM_TH-3-2THCNCT -1+3.3V, +5.1V, +24V,+24VRLow voltage powersupply circuitJ13-1-2-3High temp.detection circuitConnectingdetectioncircuitTH1TH2TP1H1J31-2-1RL1H2Heater triggercircuitHigh temp.detection circuit
